From: Dave Chinner <redacted>

The caller of xlog_write() usually has a close accounting of the
aggregated vector length contained in the log vector chain passed to
xlog_write(). There is no need to iterate the chain to calculate he
length of the data in xlog_write_calculate_len() if the caller is
already iterating that chain to build it.

Passing in the vector length avoids doing an extra chain iteration,
which can be a significant amount of work given that large CIL
commits can have hundreds of thousands of vectors attached to the
chain.

Signed-off-by: Dave Chinner <redacted>
---
 fs/xfs/xfs_log.c      | 37 ++++++-------------------------------
 fs/xfs/xfs_log_cil.c  | 18 +++++++++++++-----
 fs/xfs/xfs_log_priv.h |  2 +-
 3 files changed, 20 insertions(+), 37 deletions(-)

diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
index 412b167d8d0e..22f97914ab99 100644
--- a/fs/xfs/xfs_log.c
+++ b/fs/xfs/xfs_log.c

@@ -858,7 +858,8 @@ xlog_write_unmount_record(
 	 */
 	if (log->l_targ != log->l_mp->m_ddev_targp)
 		blkdev_issue_flush(log->l_targ->bt_bdev);
-	return xlog_write(log, &vec, ticket, NULL, NULL, XLOG_UNMOUNT_TRANS);
+	return xlog_write(log, &vec, ticket, NULL, NULL, XLOG_UNMOUNT_TRANS,
+				reg.i_len);
 }
 
 /*

@@ -1577,7 +1578,8 @@ xlog_commit_record(
 
 	/* account for space used by record data */
 	ticket->t_curr_res -= reg.i_len;
-	error = xlog_write(log, &vec, ticket, lsn, iclog, XLOG_COMMIT_TRANS);
+	error = xlog_write(log, &vec, ticket, lsn, iclog, XLOG_COMMIT_TRANS,
+				reg.i_len);
 	if (error)
 		xfs_force_shutdown(log->l_mp, SHUTDOWN_LOG_IO_ERROR);
 	return error;

@@ -2097,32 +2099,6 @@ xlog_print_trans(
 	}
 }
 
-/*
- * Calculate the potential space needed by the log vector. All regions contain
- * their own opheaders and they are accounted for in region space so we don't
- * need to add them to the vector length here.
- */
-static int
-xlog_write_calc_vec_length(
-	struct xlog_ticket	*ticket,
-	struct xfs_log_vec	*log_vector,
-	uint			optype)
-{
-	struct xfs_log_vec	*lv;
-	int			len = 0;
-	int			i;
-
-	for (lv = log_vector; lv; lv = lv->lv_next) {
-		/* we don't write ordered log vectors */
-		if (lv->lv_buf_len == XFS_LOG_VEC_ORDERED)
-			continue;
-
-		for (i = 0; i < lv->lv_niovecs; i++)
-			len += lv->lv_iovecp[i].i_len;
-	}
-	return len;
-}
-
 static xlog_op_header_t *
 xlog_write_setup_ophdr(
 	struct xlog_op_header	*ophdr,

@@ -2285,13 +2261,13 @@ xlog_write(
 	struct xlog_ticket	*ticket,
 	xfs_lsn_t		*start_lsn,
 	struct xlog_in_core	**commit_iclog,
-	uint			optype)
+	uint			optype,
+	uint32_t		len)
 {
 	struct xlog_in_core	*iclog = NULL;
 	struct xfs_log_vec	*lv = log_vector;
 	struct xfs_log_iovec	*vecp = lv->lv_iovecp;
 	int			index = 0;
-	int			len;
 	int			partial_copy = 0;
 	int			partial_copy_len = 0;
 	int			contwr = 0;

@@ -2306,7 +2282,6 @@ xlog_write(
 		xfs_force_shutdown(log->l_mp, SHUTDOWN_LOG_IO_ERROR);
 	}
 
-	len = xlog_write_calc_vec_length(ticket, log_vector, optype);
 	if (start_lsn)
 		*start_lsn = 0;
 	while (lv && (!lv->lv_niovecs || index < lv->lv_niovecs)) {

diff --git a/fs/xfs/xfs_log_cil.c b/fs/xfs/xfs_log_cil.c
index 7a5e6bdb7876..34abc3bae587 100644
--- a/fs/xfs/xfs_log_cil.c
+++ b/fs/xfs/xfs_log_cil.c

@@ -710,11 +710,12 @@ xlog_cil_build_trans_hdr(
 				sizeof(struct xfs_trans_header);
 	hdr->lhdr[1].i_type = XLOG_REG_TYPE_TRANSHDR;
 
-	tic->t_curr_res -= hdr->lhdr[0].i_len + hdr->lhdr[1].i_len;
-
 	lvhdr->lv_niovecs = 2;
 	lvhdr->lv_iovecp = &hdr->lhdr[0];
+	lvhdr->lv_bytes = hdr->lhdr[0].i_len + hdr->lhdr[1].i_len;

 	lvhdr->lv_next = ctx->lv_chain;
+
+	tic->t_curr_res -= lvhdr->lv_bytes;
 }
 
 /*

@@ -742,7 +743,8 @@ xlog_cil_push_work(
 	struct xfs_log_vec	*lv;
 	struct xfs_cil_ctx	*new_ctx;
 	struct xlog_in_core	*commit_iclog;
-	int			num_iovecs;
+	int			num_iovecs = 0;
+	int			num_bytes = 0;
 	int			error = 0;
 	struct xlog_cil_trans_hdr thdr;
 	struct xfs_log_vec	lvhdr = { NULL };

@@ -841,7 +843,6 @@ xlog_cil_push_work(
 	 * by the flush lock.
 	 */
 	lv = NULL;
-	num_iovecs = 0;
 	while (!list_empty(&cil->xc_cil)) {
 		struct xfs_log_item	*item;
 

@@ -855,6 +856,10 @@ xlog_cil_push_work(
 		lv = item->li_lv;
 		item->li_lv = NULL;
 		num_iovecs += lv->lv_niovecs;
+
+		/* we don't write ordered log vectors */
+		if (lv->lv_buf_len != XFS_LOG_VEC_ORDERED)
+			num_bytes += lv->lv_bytes;
 	}
 
 	/*

@@ -893,6 +898,9 @@ xlog_cil_push_work(
 	 * transaction header here as it is not accounted for in xlog_write().
 	 */
 	xlog_cil_build_trans_hdr(ctx, &thdr, &lvhdr, num_iovecs);
+	num_iovecs += lvhdr.lv_niovecs;
+	num_bytes += lvhdr.lv_bytes;
+
 

 	/*
 	 * Before we format and submit the first iclog, we have to ensure that

@@ -907,7 +915,7 @@ xlog_cil_push_work(
 	 * write head.
 	 */
 	error = xlog_write(log, &lvhdr, ctx->ticket, &ctx->start_lsn, NULL,
-				XLOG_START_TRANS);
+				XLOG_START_TRANS, num_bytes);
 	if (error)
 		goto out_abort_free_ticket;
 

diff --git a/fs/xfs/xfs_log_priv.h b/fs/xfs/xfs_log_priv.h
index 8ee6a5f74396..003c11653955 100644
--- a/fs/xfs/xfs_log_priv.h
+++ b/fs/xfs/xfs_log_priv.h

@@ -462,7 +462,7 @@ void	xlog_print_tic_res(struct xfs_mount *mp, struct xlog_ticket *ticket);
 void	xlog_print_trans(struct xfs_trans *);
 int	xlog_write(struct xlog *log, struct xfs_log_vec *log_vector,
 		struct xlog_ticket *tic, xfs_lsn_t *start_lsn,
-		struct xlog_in_core **commit_iclog, uint optype);
+		struct xlog_in_core **commit_iclog, uint optype, uint32_t len);
 int	xlog_commit_record(struct xlog *log, struct xlog_ticket *ticket,
 		struct xlog_in_core **iclog, xfs_lsn_t *lsn);
 void	xlog_state_switch_iclogs(struct xlog *log, struct xlog_in_core *iclog,

-- 
2.28.0